]> git.saurik.com Git - apple/xnu.git/blob - libkern/firehose/chunk_private.h
xnu-7195.81.3.tar.gz
[apple/xnu.git] / libkern / firehose / chunk_private.h
1 /*
2 * Copyright (c) 2016 Apple Inc. All rights reserved.
3 *
4 * @APPLE_APACHE_LICENSE_HEADER_START@
5 *
6 * Licensed under the Apache License, Version 2.0 (the "License");
7 * you may not use this file except in compliance with the License.
8 * You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing, software
13 * distributed under the License is distributed on an "AS IS" BASIS,
14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
15 * See the License for the specific language governing permissions and
16 * limitations under the License.
17 *
18 * @APPLE_APACHE_LICENSE_HEADER_END@
19 */
20
21 #ifndef __FIREHOSE_CHUNK_PRIVATE__
22 #define __FIREHOSE_CHUNK_PRIVATE__
23
24 #include <sys/param.h>
25 #include "firehose_types_private.h"
26 #include "tracepoint_private.h"
27
28 __BEGIN_DECLS
29
30 #define FIREHOSE_CHUNK_SIZE 4096ul
31
32 #define FIREHOSE_CHUNK_POS_ENTRY_OFFS_INC (1ULL << 0)
33 #define FIREHOSE_CHUNK_POS_PRIVATE_OFFS_INC (1ULL << 16)
34 #define FIREHOSE_CHUNK_POS_REFCNT_INC (1ULL << 32)
35 #define FIREHOSE_CHUNK_POS_FULL_BIT (1ULL << 56)
36 #define FIREHOSE_CHUNK_POS_USABLE_FOR_STREAM(pos, stream) \
37 ((((pos).fcp_pos >> 48) & 0x1ff) == (uint16_t)stream)
38
39 typedef union {
40 os_atomic(uint64_t) fcp_atomic_pos;
41 uint64_t fcp_pos;
42 struct {
43 uint16_t fcp_next_entry_offs;
44 uint16_t fcp_private_offs;
45 uint8_t fcp_refcnt;
46 uint8_t fcp_qos;
47 uint8_t fcp_stream;
48 uint8_t fcp_flag_full : 1;
49 uint8_t fcp_flag_io : 1;
50 uint8_t fcp_quarantined : 1;
51 uint8_t _fcp_flag_unused : 5;
52 };
53 } firehose_chunk_pos_u;
54
55 typedef struct firehose_chunk_s {
56 uint8_t fc_start[0];
57 firehose_chunk_pos_u fc_pos;
58 uint64_t fc_timestamp;
59 uint8_t fc_data[FIREHOSE_CHUNK_SIZE - 8 - 8];
60 } *firehose_chunk_t;
61
62 typedef struct firehose_chunk_range_s {
63 uint16_t fcr_offset; // offset from the start of the chunk
64 uint16_t fcr_length;
65 } *firehose_chunk_range_t;
66
67 #if defined(KERNEL) || defined(OS_FIREHOSE_SPI)
68
69 OS_ALWAYS_INLINE
70 static inline bool
71 firehose_chunk_pos_fits(firehose_chunk_pos_u *pos, uint16_t size)
72 {
73 return pos->fcp_next_entry_offs + size <= pos->fcp_private_offs;
74 }
75
76 #define FIREHOSE_CHUNK_TRY_RESERVE_FAIL_ENQUEUE (-1)
77 #define FIREHOSE_CHUNK_TRY_RESERVE_FAIL ( 0)
78
79 #if OS_ATOMIC_HAS_STARVATION_FREE_RMW || !OS_ATOMIC_CONFIG_STARVATION_FREE_ONLY
80 OS_ALWAYS_INLINE
81 static inline long
82 firehose_chunk_tracepoint_try_reserve(firehose_chunk_t fc, uint64_t stamp,
83 firehose_stream_t stream, uint8_t qos, uint16_t pubsize,
84 uint16_t privsize, uint8_t **privptr)
85 {
86 const uint16_t ft_size = offsetof(struct firehose_tracepoint_s, ft_data);
87 firehose_chunk_pos_u orig, pos;
88 bool reservation_failed, stamp_delta_fits;
89
90 stamp_delta_fits = ((stamp - fc->fc_timestamp) >> 48) == 0;
91
92 // no acquire barrier because the returned space is written to only
93 os_atomic_rmw_loop(&fc->fc_pos.fcp_atomic_pos,
94 orig.fcp_pos, pos.fcp_pos, relaxed, {
95 if (orig.fcp_pos == 0) {
96 // we acquired a really really old reference, and we probably
97 // just faulted in a new page
98 os_atomic_rmw_loop_give_up(return FIREHOSE_CHUNK_TRY_RESERVE_FAIL);
99 }
100 if (!FIREHOSE_CHUNK_POS_USABLE_FOR_STREAM(orig, stream)) {
101 // nothing to do if the chunk is full, or the stream doesn't match,
102 // in which case the thread probably:
103 // - loaded the chunk ref
104 // - been suspended a long while
105 // - read the chunk to find a very old thing
106 os_atomic_rmw_loop_give_up(return FIREHOSE_CHUNK_TRY_RESERVE_FAIL);
107 }
108 pos.fcp_pos = orig.fcp_pos;
109 if (!firehose_chunk_pos_fits(&orig,
110 ft_size + pubsize + privsize) || !stamp_delta_fits) {
111 pos.fcp_flag_full = true;
112 reservation_failed = true;
113 } else {
114 if (qos > pos.fcp_qos) {
115 pos.fcp_qos = qos;
116 }
117 // using these *_INC macros is so that the compiler generates better
118 // assembly: using the struct individual fields forces the compiler
119 // to handle carry propagations, and we know it won't happen
120 pos.fcp_pos += roundup(ft_size + pubsize, 8) *
121 FIREHOSE_CHUNK_POS_ENTRY_OFFS_INC;
122 pos.fcp_pos -= privsize * FIREHOSE_CHUNK_POS_PRIVATE_OFFS_INC;
123 pos.fcp_pos += FIREHOSE_CHUNK_POS_REFCNT_INC;
124 const uint16_t minimum_payload_size = 16;
125 if (!firehose_chunk_pos_fits(&pos,
126 roundup(ft_size + minimum_payload_size, 8))) {
127 // if we can't even have minimum_payload_size bytes of payload
128 // for the next tracepoint, just flush right away
129 pos.fcp_flag_full = true;
130 }
131 reservation_failed = false;
132 }
133 });
134
135 if (reservation_failed) {
136 if (pos.fcp_refcnt) {
137 // nothing to do, there is a thread writing that will pick up
138 // the "FULL" flag on flush and push as a consequence
139 return FIREHOSE_CHUNK_TRY_RESERVE_FAIL;
140 }
141 // caller must enqueue chunk
142 return FIREHOSE_CHUNK_TRY_RESERVE_FAIL_ENQUEUE;
143 }
144 if (privptr) {
145 *privptr = (uint8_t *)((uintptr_t)fc->fc_start + pos.fcp_private_offs);
146 }
147 return orig.fcp_next_entry_offs;
148 }
149
150 OS_ALWAYS_INLINE
151 static inline firehose_tracepoint_t
152 firehose_chunk_tracepoint_begin(firehose_chunk_t fc, uint64_t stamp,
153 uint16_t pubsize, uint64_t thread_id, long offset)
154 {
155 firehose_tracepoint_t ft = (firehose_tracepoint_t)
156 __builtin_assume_aligned((void *)((uintptr_t)fc->fc_start + (uintptr_t)offset), 8);
157 stamp -= fc->fc_timestamp;
158 stamp |= (uint64_t)pubsize << 48;
159 // The compiler barrier is needed for userland process death handling, see
160 // (tracepoint-begin) in libdispatch's firehose_buffer_stream_chunk_install.
161 os_atomic_std(atomic_store_explicit)(&ft->ft_atomic_stamp_and_length, stamp,
162 os_atomic_std(memory_order_relaxed));
163 __asm__ __volatile__ ("" ::: "memory");
164 ft->ft_thread = thread_id;
165 return ft;
166 }
167
168 OS_ALWAYS_INLINE
169 static inline bool
170 firehose_chunk_tracepoint_end(firehose_chunk_t fc,
171 firehose_tracepoint_t ft, firehose_tracepoint_id_u ftid)
172 {
173 firehose_chunk_pos_u pos;
174
175 os_atomic_std(atomic_store_explicit)(&ft->ft_id.ftid_atomic_value,
176 ftid.ftid_value, os_atomic_std(memory_order_release));
177 pos.fcp_pos = os_atomic_std(atomic_fetch_sub_explicit)(&fc->fc_pos.fcp_atomic_pos,
178 FIREHOSE_CHUNK_POS_REFCNT_INC, os_atomic_std(memory_order_relaxed));
179 return pos.fcp_refcnt == 1 && pos.fcp_flag_full;
180 }
181 #endif // OS_ATOMIC_HAS_STARVATION_FREE_RMW || !OS_ATOMIC_CONFIG_STARVATION_FREE_ONLY
182
183 #endif // defined(KERNEL) || defined(OS_FIREHOSE_SPI)
184
185 __END_DECLS
186
187 #endif // __FIREHOSE_CHUNK_PRIVATE__